The present invention relates generally to the field of silicon wafer fabrication equipment useful in the manufacture of semiconductor devices, more particularly to apparatus for depositing an epitaxial layer from a source gas by the chemical vapor deposition (CVD) method, and especially to improvements in the cooling and ease of servicing of such equipment.
Apparatus of the above type is used in the fabrication of semiconductor devices on 100 millimeter or larger wafers of silicon. Epitaxial layers are formed on the surfaces of the wafers by heating them to temperatures in the region of 1100 to 1200 degrees Celsius in a bell jar containing a gaseous atmosphere consisting of a hydrogen carrier gas mixed with one or more reactive gases such as a silicon source gas or a dopant source gas.
The CVD process is highly temperature sensitive, such that producing the required high quality epitaxial layers on the surfaces of the wafers while avoiding deposition on the walls of the bell jar requires that the wafers be uniformly heated to a precise temperature while the remainder of the apparatus is maintained at a temperature well below that at which the CVD reaction will occur.
The required heating of the wafers is accomplished by inductively heating the graphite susceptor on which the wafers are supported or by radiant heating with a large array of heating lamps surrounding the bell jar, while an air cooling system cools the walls of the bell jar.